First-principles study the elastic constant, electronic structure and thermoelectric properties of Zr1 − xHfxNiPb (x = 0, 0.25, 0.5, 0.75, 1)

Abstract

Based on first-principles calculations we systematically studied the electronic structure and thermoelectric properties of Zr1−xHfxNiPb (x = 0, 0.25, 0.5, 0.75, 1) compounds with TB-mBJ and TB-mBJ plus spin-orbit coupling methods. Our results indicate that these compounds are thermodynamic stabled narrow-gap semiconductors. The low frequency optical branches intersect with the acoustic modes below 75cm−1 for these artificial compounds, which enhance the phonon scattering and then decrease thermal conductivity. The Hf substitution significantly decreases the lattice thermal conductivity from 13.1Wm−1K−1 (x = 0) to 0.23Wm−1K−1 (x = 0.25) at 300 K. We confirmed that the Hf doping hardly influences the power factors S2Tσ in both of p- and n-type, but greatly decreases the thermal conductivity κ, i.e. improving the figure of merit ZT=S2Tσ/κ. The Zr0.75Hf0.25NiPb, Zr0.5Hf0.5NiPb and Zr0.25Hf0.75NiPb, with ultra low thermal conductivity (0.23, 2.2 and 0.48Wm−1K−1 at 300 K) and higher power factor, may become new candidates of high performance thermoelectric materials in both of p- and n-type.